Filtration container

ABSTRACT

A filtration container ( 1 ) comprises a container body ( 2 ) including a porous filter ( 4 ) exhibiting both hydrophilic and oleophobic properties. The container also has a lid ( 3 ) which provides a secondary filter for the container ( 1 ).

The present invention relates to a filtration container and a method oftesting the fat content of an item.

There are many situations where it is desirable to perform a compositionanalysis of a material and test procedures for determining thecomposition of a material may require several processing steps where thereagent used in one step must be thoroughly removed from the containerbefore advancing to the next step of the test. For example, it may bedesired to find the total fat content (also referred to as the Oil Bcontent) of a foodstuff. An established conventional laboratorytechnique (ISO 6492:1999) for doing this is to place a known weight of afood or foodstuff into a cellulose thimble. The food or foodstuff maythen be treated with a solvent under reflux conditions in order toremove the unbound fat therein and collected in a pre-dried and weighedreceptacle.

The next step in the process is to release bound fat from the material.This is achieved using a process wherein the solvent-treated material isquantitatively transferred to a flask and gently boiled with an acid ofknown concentration for a period of 60 minutes under reflux conditions,cooled to ambient temperature and a filtration aid added and mixed.

The contents of the flask are quantitatively transferred and filteredthrough double moistened filter papers of a pre-determined porosity andwashed with distilled water until all the acid is removed. The residueremaining is oven dried for a period of 4 hours, removed from the oven,cooled and quantitatively returned to the thimble.

The next step in the process is to remove the unbound fat from theresidue and this is achieved by subjecting the residue contained withinthe thimble to a second treatment with solvent under reflux conditionsfor a period of 5 hours, collecting the fat in a pre-dried and weighedreceptacle.

The solvent is removed from the receptacle by evaporation, thus leavingthe fat behind.

The receptacle containing the fat is dried and weighed in order todetermine the total weight of fat removed from the two treatments withsolvent under reflux conditions.

The above process is labour intensive and time-consuming, allowing onlyone test per flask to be performed. The act of transferring the residuefrom the thimble to the flask for hydrolysis may result in leaving someof the residue behind. During the transfer of the hydrolyzed residueduring the filtration process, some of the fat may be left behind. Fatmay also be left behind on the reflux vessel, resulting in the loss ofwanted constituents.

As prior art, there may also be mentioned WO99/02959.

According to a first aspect of the present invention, there is provideda filtration container comprising a container body including a porousfilter exhibiting both hydrophilic and oleophobic properties, having forexample the ability to retain fat in a hydrolysis step and release itduring a solvent extraction step.

The filtration container may be provided with a closure for thecontainer body, which closure may mechanically engage with the containerbody so as to secure the closure to close the container body at one end,for example being held in a push fit engagement with the container body.

The closure may also provide a secondary filter for the container, forexample being domed to increase the surface area of the secondaryfilter.

The porous filter may be slidable in the container body and expandableand/or rotatable.

The container body could be rigid.

The container body could be substantially cylindrical.

The container body may comprise a polymer (such as polypropylene orpolytetrafluorethylene (PTFE)) or glass.

The porous filter may comprise a polymer, for example a polyester.

The closure could comprise glass fibres or cellulose or a porous polymeror a sintered material to provide such a secondary filter.

According to a second aspect of the present invention, there is provideda method of testing a fat content of an item, comprising the steps ofplacing the item within a filtration container and then performing oneor more of the following steps.

-   -   1. solvent extraction of fat and re-weighing the container;    -   2. using a liquid to separate bound fat and removing the liquid        and soluble components from the container and, optionally,        re-weighing;    -   3. washing in water, removing the water soluble components from        the container and, optionally re-weighing the container;    -   4. drying the container to remove moisture and weighing the        container;    -   5. solvent extraction from the container and optionally weighing        the receiving receptacle; and    -   6. burning the container to remove organic matter within the        container and weighing.

According to a third aspect of the present invention, there is provideda filtration container comprising a body containing an internalfiltration membrane which retains fats during hydrolysis and washingprocedures, with an additional external filtration membrane which isadded prior to a solvent extraction procedure.

It is thus possible to provide a container which allows removal of fatspre-hydrolysis (optional) and post hydrolysis without losses of fat.Comparative data between the conventional method (ISO 6492:1999) and amethod according to the invention has shown that when using the latter,the initial solvent extraction step is unnecessary, thus savingsubstantial time.

Preferably, the container has a closure, such as a lid, such that thesample can be placed in the container and sealed therein prior to theanalysis. The closure may be held in a push fit engagement with thecontainer. Alternatively, the closure may be securely engaged with thecontainer, for example by means of co-operating screw thread portions orsome other mechanical engagement mechanism.

Advantageously, a surface of the removable lid comprises a suitablemembrane to provide such an external filtration membrane used during thesolvent refluxing processes.

The inventors have found that certain materials such as glass fibres orcellulose or a sintered material are suitable for the externalfiltration membrane of the lid due to its temperature and chemicalresistance.

Preferably the container is rigid and constructed of a material capableof withstanding high temperatures and also exhibiting chemicalresistance. Advantageously, the body of the container should alsoexhibit non-stick properties and the inventors have found that a polymer(such as polypropylene or PTFE) or glass is suitable for thisapplication.

The internal filtration membrane should be able to be re-positioned posthydrolysis, thus allowing rapid removal of water and elimination ofcondensation during drying. It should exhibit hydrophilic and alsooleophobic properties to allow rapid transmission of acid and waterduring a hydrolysis process but to retain hydrolized fats within thecontainer during emptying and washing procedures following hydrolysis.Following drying, the filter should exhibit the ability to be able to berotated to a vertical position prior to the final solvent extraction, toget a more rapid extraction. The inventors have found that a spiralconstruction using a polyester material enhances the hydrophilic natureof the internal filtration membrane and also allows the surface area ofthe membrane to be substantially increased post acid hydrolysis, whichincreases its hydrophilic properties and increases the speed of dryingthe residue and membrane prior to final solvent extraction.

It has also been found that rotation of the internal membrane prior tothe final solvent extraction improves the efficiency of the removal oftotal fats.

The external, detachable filtration membrane, which as stated above, isadvantageously part of a lid, which is initially used to contain thesample under test, must be capable of only allowing the passage of fatssolubilized within the solvent (for example petroleum ether) to passthrough it.

According to a fourth aspect of the present invention, there is provideda method of testing a fat content within an item, comprising placing theitem within a container and then performing one or more of the followingsteps:

-   -   1. solvent extraction of fat, removal of solvent from a        receiving vessel, and drying and re-weighing the receiving        vessel;    -   2. using a liquid to separate bound fat and then removing the        liquid and washing with distilled water;    -   3. drying the residue in an oven and optionally re-weighing; and    -   4. solvent extracting the hydrolysed residue, removal of the        solvent from the receiving vessel and drying and re-weighing the        receiving vessel.

The present invention will now be described, by way of example, withreference to the accompanying drawing in which:

FIG. 1 is a perspective view of a container according to an embodimentof the present invention; and

FIG. 2 is a longitudinal sectional view of the container.

A container 1 illustrated in FIGS. 1 and 2 comprises a rigid cylindricalcontainer body 2 comprising glass or a polymer such as polypropylene.The container body 2 is provided with a lid 3 which comprises a porouscellulose dome which engages with the container body 2 allowing onlysoluble components to pass through it. The domed shape is designed toincrease the surface area of the filter, thus allowing more effectivesolvent extraction.

The lid 3 has a dual purpose, firstly to contain test material in thecontainer 1 prior to analysis and secondly to separate the solublecomponents from insoluble components during solvent extraction.

The container body 2 contains a porous filter 4, the preferred designbeing a spirally wound expandable, slidable and rotatable polyesterfilter (acting as a filtration membrane) which exhibits hydrophilic andalso oleophobic properties, this not only enhancing the drying processpost hydrolysis but also the final solvent extraction. Inside thecontainer body 2 there is an internal shoulder 5, acting as a stop whenthe filter 4 is moved towards the lid 3 (see below).

In use, a sample (not shown) is introduced into the container body 2.The lid 3 is affixed to the container 1, thus trapping the sampletherein and the container is re-weighed to obtain the weight of thesample.

If the sample is a food or feed product and it is desired to determineits total fat content, a weight of the food product is placed in thecontainer 1. The sample then undergoes a hydrolysis process, whichreleases the bound fat, in the absence of the lid 3.

At completion of this stage, the water soluble phase is separated byfiltration, draining out of the container body 2, leaving behind thefats, oils and waxes and non-hydrolyzed material, which remain withinthe container body 2. The porous nature of the filter 4 retains thehydrolized fats, oils and waxes and hydrolyzed material within thecontainer body 2.

After the step of hydrolysis, e.g. by boiling in acid, has beencompleted, the container body 2 may be flushed with distilled wateruntil the material contained within the container body 2 is free ofacid. Prior to solvent extraction, it is necessary to remove the waterfrom the hydrolyzed sample and filter 4, and this is achieved by slidingand expanding the filter 4 to its upper position against the shoulder 5using a tool provided. The inventors have found that this process speedsup the drying procedure by increasing the surface area of the sample andfilter 4 and reduces condensation. For this purpose, the bottom of thecontainer body 2 may be open as shown or shaped to receive anappropriate tool.

Next, the container body 2 and its contents may be oven dried, e.g. in amicrowave oven, prior to the final stage of solvent extraction.

Prior to the final solvent extraction, the filter 4 is rotated to avertical position, this enhancing efficient solvent extraction, and thelid 3 is put in place on the container body 2.

Fats, oils and waxes (the crude (or total) fat) of the sample areremoved from the hydrolyzed material by subjecting the container and itscontents to solvent extraction, the fats, oils and waxes beingsolubilised and collected in a pre-dried and weighed receivingreceptacle which is finally dried and re-weighed. The increase in weightof the receptacle represents the total weight of fats, oils and waxescontained within the material and called in the art Oil B.

Table 1 shows various determinations of Oil B in various materials. Eachmaterial was tested using the conventional prior art method describedabove and a method according to the invention, using the above-describedcontainer. The results for the prior art Oil B method, and the methodusing the invention are each presented in columns, the left-hand columnin each case containing experimental results, and the right-hand columncontaining the averages. TABLE 2 ALL DATA IS EXPRESSED IN gms/100 gmsMATERIAL PRIOR ART THE INVENTION WHEY  0.81  0.81  0.89 (0.85)  0.87(0.84) OATS  8.84  8.58  9.21 (9.03)  8.42 (8.50) DRINKING 12.60 12.77CHOCOLATE 12.92 (12.76) 12.84 (12.81) DRIED YOGURT 10.00 10.34  9.91(9.96) 10.23 (10.29) DRIED MILK 25.27 25.69 25.88 (25.58) 25.86 (25.78)SUET 78.43 79.68 79.88 (79.16) 79.75 (79.72) SKIMMED MILK  0.79  0.99 0.69 (0.74)  0.74(0.87) FULL FAT SOYA 20.32 20.11 20.39 (20.36) 20.19(20.15) FISH MEAL 12.11 11.42 12.16 (12.14) 11.64 (11.53) WHEAT  2.22 2.18  2.21 (2.22)  2.06 (2.12) BISCUIT MEAL 14.83 15.18 14.86 (14.85)15.09 (15.14) SEMOLINA  1.58  1.56  1.49 (1.54)  1.56 (1.56) MAIZE  4.73 4.98  4.98 (4.86)  4.99 (4.99) GRASS  1.11  1.42  1.25 (1.18)  1.31(1.37)

As can be seen from the conventional prior art method, dried milk gave amean value of 25.58 gms per 100 gms of sample with a range of 0.43. Theuse of the present invention gave a mean value of 25.78 with a range of0.12. In general the use of the invention gave greater agreement betweenreplicates than the conventional prior art method.

It is thus possible to provide a filtration container for analytical usewhich functions both as a container and a filter element. This enablesthe transfer of materials to be eliminated, thereby giving an increaseto experimental accuracy. The use of container 1 also increases thecapability of a laboratory to perform many tests simultaneously.

The container 1 may, in use, be held within a rack or carousel assemblywhich aids the placement and removal of one or more containers into andout of beakers containing reagents used in the analysis.

The container may be used to perform a number of tests. An example of atest for the Oil B content of a food is described below:

-   -   1. For each test, weigh 1.5-2.0 grams of a sample into a        container body 2 and place the container 1 into a carousel which        can take several samples (e.g. 6).    -   2 . If required, independently determine the dry matter content        of each material using a standard oven drying method.    -   3. Measure out 350 mls of Hydrochloric Acid (3 molar) and        transfer to a first extraction beaker.    -   4. Lower the carousel gently into the beaker of solution and        moisten the surface of each sample with acid using a disposable        pipette.    -   5. Place the beaker on a pre-heated hotplate, replace the        condenser and bring to a gentle boil under reflux conditions.        This procedure is repeated for each set of tests.    -   6. After 1 hour from the point of boiling, remove the beaker        from the hotplate, cool to ambient temperature and remove the        carousel from the beaker and allow the containers 1 to drain.    -   7. Discard the acid and solubles within the beaker and fill with        purified water at ambient temperature. Lower the carousel into        the water, ensuring all the containers refill. Remove the        carousel and drain the containers and beaker and repeat until        the washes become neutral, which may be tested with pH test        paper.    -   8. All drained containers are placed for a few minutes on tissue        paper to remove excess water.    -   9. Using the tool provided, the internal filter 4 of each        container 1 is expanded and repositioned to its uppermost limit.    -   10. The containers containing the residues are oven dried to a        constant weight in a microwave oven to remove the water.    -   11. A filter lid 3 is fitted to each container 1, a small plug        of cotton wool inserted to retain the sample and each placed in        a solvent extraction assembly and refluxed for a specific        period. The fats, oils and waxes are collected within a        pre-dried and weighed receptacle.    -   12. Finally, the solvent is removed from each receptacle, placed        in a rack and oven dried (100° C.) to a constant weight and        re-weighed. The increase in weight is reported as Oil B.

The Oil B content can be calculated from the following equation:$\quad{\begin{matrix}{{\%\quad{Oil}\quad B\quad{in}}\quad} \\{{the}\quad{Dry}\quad{Matter}}\end{matrix} = {\frac{{Flask}\quad + {{Oil}\quad B\quad{Weight}} - {{Flask}\quad{Weight}}}{{Sample}\quad{Weight} \times {Dry}{\quad\quad}{matter}\quad{grams}\text{/}{gram}} \times {\frac{100}{1}.}}}$

1. A filtration container comprising a container body including a porousfilter exhibiting both hydrophilic and oleophobic properties.
 2. Afiltration container according to claim 1, provided with a closure forthe container body.
 3. A filtration container according to claim 2, inwhich the closure mechanically engages with the container body so as tosecure the closure to close the container body at one end.
 4. Afiltration container according to claim 3, in which the closure is heldin a push fit engagement with the container body.
 5. A filtrationcontainer according to claim 2 in which the closure also provides asecondary filter for the container.
 6. A filtration container accordingto claim 5, in which the closure is domed to increase the surface areaof the secondary filter.
 7. A filtration container as claimed in claim2, in which the porous filter is slidable in the container body andexpandable and/or rotatable.
 8. A filtration container according toclaim 2, in which the container body is rigid.
 9. A filtration containeraccording to claim 2, in which the container body is substantiallycylindrical.
 10. A filtration container according to claim 2, in whichthe container body comprises a polymer or glass.
 11. A filtrationcontainer according to claim 2, wherein the porous filter comprises apolymer.
 12. A filtration container according to claim 11, in which thepolymer is a polyester.
 13. A filtration container according to claim 5,wherein the closure comprises glass fibres or cellulose or a porouspolymer or a sintered material to provide the secondary filter.
 14. Afiltration container comprising a body containing an internal filtrationmembrane which retains fats during hydrolysis and washing procedures,with an additional external filtration membrane which is added prior toa solvent extraction procedure.
 15. A method of testing a fat content ofan item, comprising the steps of placing the item within a containeraccording to claim 2 and then performing one or more of the followingsteps:
 1. solvent extraction of fat and re-weighing the container; 2.using a liquid to separate bound fat and removing the liquid and solublecomponents from the container and, optionally, re-weighing;
 3. washingin water, removing the water soluble components from the container and,optionally re-weighing the container;
 4. drying the container to removemoisture and weighing the container;
 5. solvent extraction from thecontainer and optionally weighing the receiving receptacle; and 6.burning the container to remove organic matter within the container andweighing.
 16. A method of testing a fat content within an item,comprising placing the item within a container according to claim 2 andthen performing one or more of the following steps:
 1. solventextraction of fat, removal of solvent from a receiving vessel, anddrying and re-weighing the receiving vessel;
 2. using a liquid toseparate bound fat and then removing the liquid and washing withdistilled water;
 3. drying the residue in an oven and optionallyre-weighing; and
 4. solvent extracting the hydrolysed residue, removalof the solvent from the receiving vessel and drying and re-weighing thereceiving vessel.
 17. A method of testing a fat content of an item,comprising the steps of placing the item within a container and thenperforming one or more of the following steps:
 1. solvent extraction offat and re-weighing the container;
 2. using a liquid to separate boundfat and removing the liquid and soluble components from the containerand, optionally, re-weighing;
 3. washing in water, removing the watersoluble components from the container and, optionally re-weighing thecontainer;
 4. drying the container to remove moisture and weighing thecontainer;
 5. solvent extraction from the container and optionallyweighing the receiving receptacle; and
 6. burning the container toremove organic matter within the container and weighing.
 18. A method oftesting a fat content within an item, comprising placing the item withina container and then performing one or more of the following steps: 1.solvent extraction of fat, removal of solvent from a receiving vessel,and drying and re-weighing the receiving vessel;
 2. using a liquid toseparate bound fat and then removing the liquid and washing withdistilled water;
 3. drying the residue in an oven and optionallyre-weighing; and
 4. solvent extracting the hydrolysed residue, removalof the solvent from the receiving vessel and drying and re-weighing thereceiving vessel.